Lapping tool



Patented Sept. 21, 1943 LAPPING TOOL Foster F. Hillix, Lakewood, Ohio,assignor to The American Steel and Wire Company of New Jersey, acorporation of New Jersey Original application April 10, 1939, SerialNo. 267,127. Divided and this application August 15, 1942, Serial No.454,991

Claims.

This invention relates to improvements in lapping tools to be employedwith granular abrasives for iinishing hard objects, such as steelmetal-Working rolls and the like, this application being a division ofmy pending application, Serial No. 267,127, iiled April 10, 1939.

It is a prime object of my invention to provide a lapping tool or blockwhich will uniformly distribute and apply a granular abrasive Withoutbunching, particularly with respect to the ends of the tool.

I have discovered that such undesirable bunching occurs with laps havinga square end, that is, having all lap faces of the same length, thegrain passing under the lap and causing accumulation and bunching of toomuch grain at the lap's end. It was at first concluded that thisdifficulty could be solved by chamfering the lap ends so as to permitthe grain to slide under the lap and the lap to slide up and over thegrains, but it was found that this idea did not work out entirelysatisfactorily.

It was nally concluded that sharp ends on the lap prevented too much ofthe grain from entering thereunder, in itself a desirable condition, butwould, in the absence of means to prevent lt, cause bunching of thegrain at the lap ends, an undesirable condition. The first of theseconditions, being desirable was retained, while the undesirable bunchingeffect was circumvented by relieving the land of the lap on one of itscorners so as to provide the end thereof with an oblique face. Thisconstruction tends to pass the grain down along the end of the lap fromland to land, admitting as much of it beneath the latter as isnecessary, and by-passing the rest completely around the end andharmlessly to one side.

This improved lapping block construction may be better understood byreference to the attached drawing in which Fig. 1 represents a plan viewof a typical block embodying the principles of the present invention;Fig. 2 being a cross-section thereof taken at line II-II, Fig. 1 Fig. 3is a side-elevational View of the block as viewed from the left in Fig.1.

In its preferred form, the block or tool may be composed of a body I offriable metal, as for example, a metal of the character described in mysaid parent application, although the benefits derivable from itsoblique ends are not limited thereto, but extend to blocks used in anylapping operation; particularly, those in which loose grain is fed tothe block on the work as described in my co-pending application, SerialNo. 208,661, filed May 18, 1938.

The working faces of the blocks comprise lands 2, between which occurthe valleys or grooves 3 into which cuttings and grain are, in part,retired, but which are provided principally to introduce lubricant andgrain uniformly throughout the entire areas of the lapping faces. Thelands 2 are progressively shortened to provide oblique ends 4 on theWork faces for reasons already set forth above.

Where the trend of movement of the block during a lapping operation isuni-directional of its axis, only the lead end need be cut away.However, since lapping operations are usually attended bypoly-directional motion of the block, and, in the case of my previousinventions, above identified, the blocks are rapidly vibrated in axialdirections, it is desirable to bevel both ends, as shown. In thisconnection, it should be noted that it is the corners of either theleading or trailing edge or side of the block that are truncated to givethis effect, i. e., leading or trailing with respect to its advancementpast the work with which it has relative movement.

This arrangement is adopted because the grain is applied to the work atthe approach side of the block, and the latter, by reciprocating,scatters all grain not carried beneath it to the left and right untilthe oblique edges are reached. Here the grains that do not actually gounder the block are rolled down from land to land, until dischargedaround the trailing corners thereof. The end-edges 5 of the lands aremaintained as sharp corners to prevent more than one diameter of grainfrom entering between the lands and the work at one time. Thus isbunching of the grain precluded, and the depth of effective cuttinggrain maintained at a minimum, whereby only constant cuts of uniformmagniture are made.

When composed of a friable metal of the character stated, the body Iwill have pores, voids, interstices, and/or grain boundaries, which,although too minute to be revealed to the naked eye, are, in fact, thespaces into which cuttings and grain are retired so as to leave theintermediate areas of metal clear of accumulations that ultimatelybunch, become impacted, and scarify the Work. These minute areas ofmetal, when properly seasoned by use, become flat on top and chargedwith grains of the abrasive. It is this condition, when the grain isconstrained to a depth of but one grain-diameter, that produces thehighestl finishes. The effectiveness of these microscopic quantitiesmight be questioned until it is realized that the abrasive grainemployed is often as ne as one fty-thousandth of an inch in diameter,and the cuttings resulting therefrom of equally small magnitude.

The lap surfaces or lands 2 are thus composed of microscopic humps andhollows, which, by virtue of their metal composition, are maintained inthis condition of greatest effectiveness due to their ability todisintegrate and wear away before becoming over-charged, impacted anduseless.

The grooves 3 between the lands 2 are suitably proportioned relative tothe latter so as to admit plenty of lubricant to the zones of work. Thelands themselves must be of suihcient thickness to provide the strengthrequired to maintain them in operation, but not so thick as to precludelubricant from reaching the central portions thereof, since the lack oflubricant promotes seizing. bunching, impacting, and scarification ofthe work. A suitable width, susceptible of some variation, isone-sixteenth of an inch for the lands, and about the same amount forthe valleys or grooves 2.

Various changes and modifications are contemplated within the scope ofthe following claims.

I claim:

l. A lapping tool or the like comprising a body having a working faceincluding a plurality of alternate uni-directional lands and groovesextending throughout said iace, the said lands having adjacent endsdisposed in oblique relation with respect to the said direction of thelands and grooves.

2. A lapping tool or the like comprising a polygonal body having aworking face including a plurality of alternate uni-directional landsand grooves extending longitudinally throughout said face, at least oneend face of the body being beveled transversely of the said lands andgrooves to progressively shorten said lands.

3. A lapping tool or the like comprising a polygonal body having aworking face including a plurality of alternate un-directional lands andgrooves extending longitudinally throughout said face, at least one endface of the body being beveled transversely of the said lands andgrooves to progressively shorten said lands, the corners of the landsformed by the lands and grooves being sharp to restrict access to saidgrooves from said end face of the body.

4. A lapping tool or the like comprising a polygonal body having aworking face ineluding a plurality of alternate uni-directional landsand grooves extending longitudinally throughout said face, both of theend faces of the body being beveled transversely of the said lands andgrooves to progressively shorten said lands.

5. A lapping tool or the like comprising a body having a working faceincluding a plurality of alternate uni-directional lands and groovesextending throughout said face, the said lands being composed of afriable metal composition and having adjacent ends disposed in obliquerelation with respect to the said direction of the lands and grooves.

FOSTER F. HILLIX.

